1. Field of the Invention
The present invention relates to positive feed tools, such as right angle positive feed drills, and more particularly, to a method and apparatus for retracting a spindle of the drill by actuating a valve.
2. Description of the Related Art
Positive feed tools, such as positive feed drills are conventionally known for drilling holes in workpieces formed of substances, such as steel, aluminum, titanium, and composites. Positive feed drills include a drill feed mechanism that feeds a drill bit into the workpiece.
During drilling with positive feed drills, cutting chips are generated when the drill bit penetrates through the workpiece. These chips may affect the final dimension of the drilled hole if they are not removed during the drilling process. Additionally, the cutting chips occasionally cease the drill bit, which may damage the spindle, gears, bearings, or other components of the drill.
One technique for removing chips during drilling is called "peck drilling." Peck drilling refers to a drilling technique whereby the rotating drill bit is advanced and then occasionally or periodically retracted to remove the cutting chips from the drilled hole and the flutes of the drill bit.
Some positive feed drills include a mechanism by which an operator of the positive feed drill can cause the spindle of the drill to retract.
For example, one conventional positive feed drill includes a retract lever. The spindle of the drill may be manually retracted by the operator physically pulling the retract lever up, in a direction away from the tool. With this conventional drill the spindle will continue to retract until the retract lever is physically pushed back down again, in a direction toward the tool. When the retract lever of this tool is pulled up, the differential feed gear of the tool is mechanically disengaged from the differential drive gear of the tool. Additionally, the differential feed gear is prevented from rotating when the retract lever is pulled up. Because the differential feed gear is prevented from rotating, the spindle will retract. However, with this technique of retracting the spindle, the retract lever must be manually forced down after the desired amount of retracting has occurred. This is problematic because the retract lever is necessarily located near the head of the drill, where the spindle and drill bit are rotating. Thus, many operators of such drills are wary of repeatedly moving the retract lever to peck drill.
Another conventional right angle positive drill also includes a manual retract lever near the spindle of the drill, which must be lifted upward to retract the spindle. When the spindle fully retracts, the motor of the tool is shut down. With this conventional drill, the spindle cannot be advanced after the retract lever has been pulled, unless the tool is completely shut off either manually or by permitting the spindle to fully retract, which will automatically shut off the motor of the tool. Only after the spindle has fully retracted and the motor has been shut down can an operator cause the spindle to once again advance toward the workpiece. Thus, it is very difficult for an operator of this conventional drill to remove cutting chips by peck drilling.
Thus, it is apparent that conventional positive feed drills are not well suited for peck drilling, and thus occasionally suffer from the problems associated with cutting chips, namely ceased spindles and galled holes. The above-described constraints and problems associated with conventional positive feed tools has created a need for a positive feed tool that may be used to peck drill more easily than conventional positive feed drills.